Competitive and noncompetitive inhibition Knowledge-Based Download PDF

Questions

1. 1.

   What structural consequence occurs when a noncompetitive inhibitor binds to an enzyme, thereby reducing catalytic activity even if the substrate remains bound?

   • A) It hydrolyzes the peptide bonds surrounding the active site cavity.
   • B) It directly occupies the catalytic pocket, physically displacing the substrate.
   • C) It causes complete, irreversible denaturation of the enzyme's tertiary structure.
   • D) It induces an allosteric conformational change that impairs the catalytic positioning of active site residues.
2. 2.

   Which molecular complex can form during noncompetitive inhibition, but cannot assemble during competitive inhibition?

   • A) Enzyme-substrate (ES) complex
   • B) Enzyme-inhibitor (EI) complex
   • C) Enzyme-product (EP) complex
   • D) Enzyme-substrate-inhibitor (ESI) complex
3. 3.

   In an enzyme-catalyzed reaction, how does the addition of a competitive inhibitor specifically alter the kinetic parameters of the enzyme?

   • A) It increases the apparent $K_m$ of the enzyme while leaving the $V_{max}$ unchanged.
   • B) It decreases the $V_{max}$ of the reaction while leaving the apparent $K_m$ unchanged.
   • C) It decreases both the apparent $K_m$ and the $V_{max}$ of the enzyme-catalyzed reaction.
   • D) It increases the $V_{max}$ while decreasing the apparent $K_m$ of the enzyme.
4. 4.

   Which statement accurately differentiates a noncompetitive inhibitor from a competitive inhibitor in an enzyme-catalyzed reaction?

   • A) It binds to an allosteric site rather than the active site, altering the enzyme's conformation so catalysis is impaired.
   • B) It binds directly to the catalytic active site, preventing substrate molecules from entering.
   • C) It binds specifically to the substrate molecules in solution, preventing them from interacting with the active site.
   • D) It irreversibly denatures the primary polypeptide backbone of the enzyme, permanently destroying its structure.
5. 5.

   How does a substantial increase in substrate concentration affect the rate of an enzyme-catalyzed reaction in the presence of a competitive inhibitor compared to a noncompetitive inhibitor?

   • A) It overcomes noncompetitive inhibition by displacing the inhibitor from the allosteric site, but it cannot reverse competitive inhibition.
   • B) It overcomes both types of inhibition equally because high substrate concentrations completely saturate all enzyme molecules.
   • C) It overcomes competitive inhibition by outcompeting the inhibitor for the active site, but it cannot reverse noncompetitive inhibition.
   • D) It has no effect on competitive inhibition because the inhibitor binds irreversibly, but it restores full activity during noncompetitive inhibition.